CN102031501A - Method for selectively depositing thin film on substrate by utilizing atomic layer deposition - Google Patents

Abstract

The present invention relates to thin film deposition technology for the preparation of semiconductor devices. It specifically relates to a method for selectively growing silicon, germanium silicon and derivative thin films on a substrate by atomic layer deposition technology. The present invention is aimed at a substrate composed of semiconductor wafers and oxide films of different density patterns. During the growth process, the substrate is heated to a predetermined temperature, and the film is grown on the surface by atomic layer deposition. The reaction precursor is doped with HCl or HCl pulses are introduced independently during the process to achieve the inhibitory effect of film growth on the oxide layer. The present invention deposits thin film in selected area, and does not deposit in other unneeded places; Can solve the thin film deposition method of the loading effect of traditional selective deposition growing on the surface of different density pattern; Do not need to use traditional Photolithography technology, and the subsequent film etching process that needs to be introduced because of the use of traditional photolithography technology.

Description

A method for selective atomic layer deposition of thin films on substrates

technical field

The invention relates to a thin film deposition technology for semiconductor device preparation. It specifically relates to a method for selective atomic layer deposition of thin films on a substrate

Background technique

Advanced thin film preparation technology is one of the key technologies for the scaling down of semiconductor devices. The proportional reduction of semiconductor devices is not only the reduction of traditional device structures, but also the introduction of new materials and device structures at the technology node of each integrated circuit. Through the above two points, the improvement of device performance at each technology node predicted according to Moore's Law can be maintained. the

Commonly used techniques for preparing thin films include sputtering, chemical vapor deposition, sol-gel method, physical vapor deposition, organic metal source chemical vapor deposition, and atomic layer deposition. Atomic layer deposition is also called atomic layer epitaxy or atomic layer chemical vapor deposition. Different from the traditional chemical vapor deposition of continuous growth, atomic layer deposition is a deposition method of alternating growth of monoatomic layer or sub-monoatomic layer. The remarkable advantage of atomic layer deposition is that the surface reaction in atomic layer deposition has a saturated characteristic, which makes the growth mode of atomic layer deposition self-limiting. Therefore, ALD has excellent large-scale uniformity, excellent conformality, and control of film composition and thickness at the atomic level. The use of atomic layer deposition to grow thin films is becoming more and more important in the fabrication of modern semiconductor devices. the

Usually, a processed substrate usually includes different films, such as dielectrics, semiconductors, and conductors. In the prior art, a non-selective process is usually used to prepare thin films: that is, thin films are grown on the entire surface of the substrate, while different materials on various parts of the substrate surface are ignored. Selective thin film growth refers to a thin film deposition method that only grows on a certain material and does not grow on the surface of other materials of the substrate. the

Selective thin film growth is an important technology in the preparation of semiconductor devices. It can not only simplify the preparation process of devices, but also greatly improve the ability to realize new device structures. In recent years, a large number of technologies for selectively depositing silicon and germanium silicon thin films are being extensively studied by researchers. For example, the technology of selective epitaxial growth of germanium and silicon thin films in the source and drain regions of advanced p-type semiconductor field effect transistors has made great progress and development. The germanium-silicon film deposited by chemical vapor phase only grows on the exposed silicon surface of the substrate, not on the silicon oxide and silicon nitride near the silicon surface. This process of selectively depositing silicon-germanium thin films is realized by introducing HCl gas into the process to suppress the nucleation of silicon-germanium thin films on the oxide and nitride surfaces. However, studies have found that this method of selectively depositing germanium-silicon thin films has a loading effect on the oxide and nitride surfaces with high-density patterns. There are two so-called load effects: the growth mode of chemical vapor deposition on the surface of high-density patterned nitride and oxide is different from that on the flat silicon wafer, which is called the global load effect, which is mainly manifested in the same Under the advanced chemical vapor deposition process, on high-density patterned substrates and planar substrates, the inhomogeneity of the doping concentration, composition and thickness of the resulting film; another related effect is the local loading Effect, this effect is manifested in different film properties (such as doping concentration, film composition and thickness) due to different pattern densities on the surface of oxides and nitrides with different structures, which are different due to different pattern densities A huge problem is introduced in terms of device fabrication technology. the

Relevant studies have tried many methods to reduce or suppress the loading effect in the process of selectively depositing silicon and silicon germanium thin films. However, these methods and processes usually bring huge process complexity and cost, and it is difficult to be widely used in the preparation. the

The shortcomings of the above growth process have brought great problems in the current nanoscale process preparation technology of integrated circuits. the

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, to provide a thin film deposition technology for the preparation of semiconductor devices, in particular to a method for selective atomic layer deposition of thin films on a substrate, especially to a A method for selectively growing silicon, silicon germanium and their derivatives by atomic layer deposition. the

One of the objects of the present invention is to use selective atomic layer deposition to deposit thin films in selected areas without depositing in other undesired areas. the

The second object of the present invention is to provide a film deposition method that can solve the loading effect of traditional selective deposition on surfaces with different density patterns. the

The third object of the present invention is to provide a method for selective atomic layer deposition of thin films without using traditional photolithography techniques and subsequent thin film etching processes that need to be introduced due to the use of traditional photolithography techniques. the

In order to achieve the above objectives, the present invention proposes a novel method for selective film growth. The method of the present invention is mainly aimed at substrates composed of semiconductor wafers and oxide films of different density patterns. During the growth process, the substrate is usually heated to a predetermined temperature, and the film is grown on the surface by atomic layer deposition. The reaction precursor for layer deposition is doped with HCl or a pulse of HCl is introduced independently during the process to achieve the inhibitory effect of film growth on the oxide layer. the

In the present invention, the inhibition of HCl on the nucleation of thin films on the surface of oxides or nitrides can be realized by heating HCl gas or plasma treatment of HCl, and the plasmaization of HCl can be performed in the reaction chamber of atomic layer deposition Produced directly, it can also be produced in a separate chamber and then transferred to the reaction chamber. the

In the present invention, the etching rate of the film grown on the surface of the insulator by HCl gas is greater than the etching rate of the film grown on the surface of the semiconductor. the

In the present invention, the wafer or substrate refers to a semiconductor substrate with graphic structures prepared on its surface. Specifically, the substrate includes a semiconductor wafer and structures and films prepared on the wafer during the process. The substrate includes silicon and oxide surfaces. the

In the atomic layer deposition process, the reaction precursors that are gaseous, liquid or solid at room temperature are usually vaporized, and then alternately passed into the reaction chamber containing the substrate. Both liquid and solid reaction precursors need to be vaporized before being introduced into the reaction chamber. In the atomic layer deposition process, each time a reactive precursor is introduced, it is called a pulse. During the pulse, the reactive precursor enters a specific region within a short period of time and undergoes a self-limiting reaction with the substrate. Between pulses, the reaction chamber is flushed with other gases, such as inert gases such as nitrogen or argon. In the present invention, the reactive precursor used for selective atomic layer deposition mainly refers to the reactive precursor containing silicon or germanium, no matter it is commercial or laboratory synthesized. Specifically, these reaction precursors may be SiH4, SiH3Cl, SiH2Cl2, SiHCl3, SiCl4, Si2H6 and other silicon-containing reaction precursors and GeH4, Ge2H6 and other germanium-containing reaction precursors. the

In the self-limited chemical adsorption ALD process, during each pulse, the reaction precursor reacts with the substrate surface in the form of chemical adsorption on the substrate, and then reaches saturation. SiCl4 is taken as an example in the present invention. Next, excess SiCl4 and by-products in the adsorption process are purged by passing inert gas such as nitrogen or argon. the

During the second pulse of ALD, a second reactive precursor is introduced into the reaction chamber to react with the substrate surface formed during the first pulse. Here, SiH4 can be introduced to grow Si film, or GeH4 can be used to grow GeSi. Next, the redundant second reaction precursor and the by-products in the adsorption process are also purged by feeding inert gases such as nitrogen or argon. By selecting reactive precursors that are easily adsorbed and reacted on the substrate, an ALD cycle can be completed in less than 1 second in a fluid reaction chamber. Typically, the pulse time for reactive precursors is between 0.5 seconds and 3 seconds. the

In the atomic layer deposition process, the saturation characteristics of all adsorption reactions and the introduction of the purge process make the growth of the film self-limited. The self-limiting growth characteristics make the thin films prepared by atomic layer deposition process have good uniformity and conformality in a wide range. This feature has very important application value in large-area substrate and deep trench technology. The atomic layer deposition process can precisely control the thickness of the film by controlling the number of growth cycles. the

In the atomic layer deposition process, the reaction precursors can be gaseous (such as SiH4), liquid (such as SiHCl3 and SiCl4), or solid at room temperature. Nevertheless, liquid and solid reaction precursors must be able to volatilize. Their saturated vapor pressure must be high enough to be able to volatilize enough reaction precursors to participate in the reaction. Therefore, some solid and liquid reaction precursors with low saturated vapor pressure need to be heated to generate enough gaseous reaction precursors to participate in the reaction. However, the heating temperature cannot exceed the substrate temperature (ie, the reaction temperature) to prevent condensation of the reaction precursors on the substrate. Due to the self-limiting nature of atomic layer deposition, some solids with lower saturated vapor pressure can also be used as reaction precursors, although these solids will react with precursors in each pulse due to the change of solid surface area. The rate of evaporation will vary. the

The reactive precursors used in atomic layer deposition have some other characteristics. The reaction precursor must be stable in the range of substrate temperature, because the self-limiting property of atomic layer deposition depends on the saturation reaction of the substrate surface, and the thermal decomposition of the reaction precursor will destroy the saturation reaction of the substrate surface . Of course, the reaction precursor only slightly decomposes, which is very small compared with the rate of atomic layer deposition, so it can be considered within the tolerance range. the

The problem solved by the invention is how to realize the selective atomic layer deposition process, that is, there is film growth in the required area, and no film growth occurs in the adjacent unnecessary area. The biggest advantage of the present invention is that the selective atomic layer deposition process can solve the load effect of selective deposition in the stacked structure composed of semiconductor substrate and nanoscale patterned insulating medium. the

Generally speaking, when the aforementioned reactive precursors such as silane are used, the nucleation of silicon on the oxide or nitride surface is much more difficult than on the silicon surface, while germanium cannot be deposited basically. During the atomic layer deposition process, the introduction of gas containing HCl helps to further suppress the growth of silicon and germanium on the oxide and nitride surfaces. Therefore, selective atomic layer deposition growth of silicon and silicon germanium can be achieved by introducing a gas containing HCl. On this basis, due to the self-limiting characteristics of atomic layer deposition, the present invention can realize semiconductor substrates and nanoscale patterned insulating media with no load effect or only slight load effect by controlling the reaction conditions, including the content of HCl gas, etc. Selective growth of silicon and germanium on stacked structures. the

Another process of the present invention to achieve selective atomic layer deposition growth is achieved by introducing an additional step of using plasma HCl to etch unwanted films. This step is added after each ALD cycle or some ALD cycles. Plasma HCl can be directly formed in the reaction chamber of atomic layer deposition, or can be formed in an independent chamber, and then transported to the reaction chamber of atomic layer deposition. This step is introduced to etch away silicon and silicon germanium formed on the oxide or nitride surface. Etching of silicon and germanium grown on semiconductor surfaces by plasma HCl can be suppressed by optimizing etch time, HCl concentration, plasma power, substrate temperature, and chamber pressure. the

The content and features of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. the

Description of drawings

Figure 1 is an example of the first process of selective atomic layer deposition of silicon or silicon germanium on a substrate. the

Fig. 2 is a second process example of selective atomic layer deposition of silicon or silicon germanium on a substrate. the

Fig. 3 is a third process example of selective atomic layer deposition of silicon or silicon germanium on a substrate. the

4-6 are side views of a silicon thin film or a silicon germanium thin film growing on a substrate during selective atomic layer deposition of silicon or silicon germanium. the

Detailed ways

Example 1

Figure 1 is a flow chart of the process of selectively depositing silicon and silicon germanium by atomic layer deposition. The oxides mentioned in the figure can be replaced by nitrides in some applications. First, the substrate is placed in the ALD reaction chamber. At 110, a silicon-containing reactive precursor, such as SiH2Cl2 or SiCl4, is introduced at the substrate. SiH2Cl2 or SiCl4 will be adsorbed on the substrate surface. Then, at 115, a purge gas is introduced into the reaction chamber. Nitrogen, argon or other inert gases can be used as purge gas. At 120, a second reactive precursor is passed into the reaction chamber. This reactive precursor can be SiH4 or GeH4. The second reaction precursor reacts with the Si-Cl group or other groups formed on the surface of the first reaction precursor to form HCl and the silicon or silicon germanium film we need. In Figure 1, selective deposition is achieved by mixing HCl gas into the second reactive precursor. HCl gas will inhibit the nucleation of silicon or silicon germanium films on oxide or nitride surfaces. Similarly, HCl gas can also be introduced into the reaction chamber together with the second reaction precursor in the form of plasma, so that HCl is more active at the lower reaction temperature of ALD, and inhibits the reaction between oxides and The ability to nucleate on the nitride is also stronger. Then, at 125, another purge gas is passed into the reaction chamber. The above cycle steps from 110 to 130 will continue until the thickness required by the process is reached. The atomic layer deposition process ends at 140 . the

It should be pointed out here that the HCl gas is not limited to be introduced into the reaction chamber together with the second reaction precursor. HCl gas can also be introduced into the reaction chamber together with the first or with the two reaction precursors. the

Example 2

Fig. 2 is a process flow chart of the second selective deposition of silicon and silicon germanium by atomic layer deposition method. the

First, similar to FIG. 1 , the process flow starts from 205 , that is, a substrate including a semiconductor wafer and a patterned oxide. In some applications, the oxides can be replaced by nitrides. The processed substrate is placed in the atomic layer reaction chamber as in FIG. 1 . At 210, silicon-containing reactive precursors, such as SiH2Cl2 and SiCl4, are passed into the reaction chamber to reach the substrate surface. SiH2Cl2 and SiCl4 will be adsorbed on the substrate surface. Then, at 215, a purge gas is introduced into the reaction chamber. Nitrogen, argon or other inert gases can be used as purge gas. The difference from Figure 1 is that in Figure 2, the HCl gas is not introduced into the reaction chamber together with the reaction precursor 2, but the introduction of HCl is realized through an independent pulse. The HCl pulse at 220 is added before reaction precursor two, pulse 225 . The second reaction precursor can be silane or germane, which reacts with the Cl group from the first reaction precursor SiH2Cl2 or SiCl4 to form the required silicon or silicon germanium film and the by-product HCl. Similar to FIG. 1 , HCl can be introduced into the reaction chamber in the form of plasma so that it can nucleate silicon or silicon germanium on the oxide or nitride surface at a lower temperature. What needs to be pointed out here is that the pulse of HCl is independently controlled, and it can be introduced at the same time before the reaction precursor 2, or after the reaction precursor 2. Also, the HCl pulses can be freely switched on and off during the ALD process. After 230, the purge gas is passed into the reaction chamber a second time. The above cycle steps from 210 to 235 will continue until the thickness required by the process is reached. The atomic layer deposition process ends at 240 . the

Example 3

Fig. 3 is a process flow diagram of the third selective deposition of silicon and silicon germanium by atomic layer deposition method. As shown in FIG. 1 , the process flow starts from 305 , which is a substrate including a semiconductor wafer and patterned oxide. In some applications, the oxide inside can be replaced by a nitride. The processed substrate is placed in the atomic layer reaction chamber in the same process as in FIG. 1 . At 310, silicon-containing reactive precursors, such as SiH2Cl2 and SiCl4, are passed into the reaction chamber to reach the substrate surface. SiH2Cl2 and SiCl4 will be adsorbed on the substrate surface. Then, at 315, a purge gas is introduced into the reaction chamber. Nitrogen, argon or other inert gases can be used as purge gas. At 320, a second reactive precursor is passed into the reaction chamber. This reaction precursor can be SiH4 or SiH2Cl2. The second reaction precursor reacts with the Si-Cl group or other groups formed on the surface of the first reaction precursor to form HCl and the silicon or silicon germanium film we need. Then, at 325, the purge gas is passed into the reaction chamber a second time. The difference from Figure 1 and Figure 2 is that here, HCl participates in the atomic layer deposition process as an independent reaction source, and it needs to be purged by inert gas between its pulse and the pulse of the reaction precursor. separate. Similar to Figure 1, HCl can be introduced into the reaction chamber in the form of plasma to achieve the reaction at a lower temperature. the

Example 4

An example of selective atomic layer deposition will be illustrated in FIGS. 4 to 6 based on the flowcharts of FIGS. 1 to 3 . At 336, a third pulse of purge gas is introduced into the reaction chamber. It should be pointed out here that the pulse of HCl can be preceded by the pulse of the reactive precursor 2 or after the pulse of the reactive precursor 2. Also, the HCl pulses can be freely switched on and off during the ALD process. The above cycle steps from 310 to 340 will continue until the thickness required by the process is reached. The atomic layer deposition process ends at 345 . the

FIG. 4 is an example of a substrate 400 mentioned in the present invention. The substrate 400 includes a semiconductor wafer 401, such as silicon, and a patterned insulator film 402, such as SiO2, thereon. Here, semiconductor wafers do not just refer to silicon wafers. The semiconductor wafer may also be a semiconductor substrate such as an SOI wafer, a Ge sheet or a GaAs sheet. It should be pointed out here that FIG. 4 is a simplified side view of the substrate 400 and only includes a part of the actual substrate. the

Before performing the atomic layer deposition process, the substrate in FIG. 4 may be subjected to etching in HF or other surface treatment methods, including standard RCA cleaning process or other cleaning processes. Then, the substrate 400 is placed in the ALD reaction chamber. As shown in FIG. 5 , the silicon thin film 403 is only deposited on the silicon surface of the substrate 400 through several cycles of ALD cycles. Here, the atomic layer deposited silicon thin film 403 may be a silicon thin film of subatomic layer, atomic layer or several atomic layers. On the insulator 402, due to the selective growth effect caused by the introduction of HCl gas, no silicon film will be deposited. the

FIG. 6 is a side view of a silicon thin film 404 and a substrate 400 with a specified thickness obtained through selective atomic layer deposition. As shown in FIG. 4 , a substrate 400 includes a semiconductor wafer 401 and an insulator film 402 patterned thereon. It should be noted here that the thin film 404 is not limited to silicon. Other thin films such as silicon germanium, germanium and other semiconductor materials can be prepared by the aforementioned method. the

The above-mentioned selective ALD silicon and germanium silicon preparation method can also be derived to the real-time doping of silicon and germanium silicon thin films. In this case, the reactive precursors for doping may be PH3 and AsH3 as n-type doping, and B2H6 as p-type doping. These reaction precursors can be introduced simultaneously with the aforementioned silane or germane when depositing silicon and germanium, or they can participate in the reaction process of atomic layer deposition through an independent pulse. Even so, all the different processes mentioned above need to pass HCl gas to realize the selective growth of silicon and silicon germanium. the

It should be pointed out here that the above-mentioned various processes and methods can be combined according to different actual applications, that is, the above-mentioned process steps and methods can be adjusted accordingly as required. This application will cover modifications and adaptations of the processes used in the specific examples discussed herein. the

Claims (18)

1. the method for a selectivity atomic layer deposition film on substrate, it is characterized in that, at the substrate of forming by the sull of semiconductor wafer and different densities figure, in process of growth, substrate is heated to preset temperature, the method of utilizing atomic layer deposition is at the surface growth film, is implemented in the retarding effect of zone of oxidation upper film growth by the pulse of mixing a kind of gas or independently introduce a kind of gas in the reacting precursor of atomic layer deposition in technological process; Described retarding effect is to carry out optionally film growth and do not grow at insulator surface at semiconductor surface.

By claim 1 described on substrate the method for selectivity atomic layer deposition film, it is characterized in that described gas is HCl, it is to the etch rate of the film of the insulator surface growth etch rate greater than the film of growing on semiconductor surface.

By claim 1 described on substrate the method for selectivity atomic layer deposition film, it is characterized in that said substrate comprises silicon and oxide surface.

By claim 1 described on substrate the method for selectivity atomic layer deposition film, it is characterized in that the film of said growth is a silicon.

5. by the described method of claim 4, it is characterized in that said silicon film is by the method preparation of atomic layer deposition, wherein employed reacting precursor is selected from SiH2Cl2, SiH4, SiHCl3, SiH3Cl, SiCl4 or Si2H6.

6. by the described method of claim 1, it is characterized in that the film of said growth is a germanium silicon.

7. by the described method of claim 6, it is characterized in that the germanium-silicon thin membrane of said growth is by the preparation of atomic layer deposition method, its reacting precursor contains GeH4 or Ge2H6 at least.

8. by the described method of claim 1, it is characterized in that said HCl passes through plasma bodyization.

9. by the described method of claim 8, it is characterized in that the HCl of said plasma bodyization is in atomic layer deposition reactions chamber ionic medium bodyization.

10. by the described method of claim 8, it is characterized in that the HCl of said plasma bodyization is in discrete cavity ionic mediumization, is passed into the atomic layer deposition reactions chamber then.

11., it is characterized in that the gas of said feeding is passed in the reaction chamber by a kind of reacting precursor that needs only in the atomic layer deposition process, forms needed film then by the described method of claim 1.

12. by the described method of claim 1, it is characterized in that, the gas source of said feeding at least with atomic layer deposition in a kind of pulse process of employed reaction source have overlapping in time.

13., it is characterized in that employed any reaction source does not all have overlapping in pulse process in time in the gas source of said feeding and the atomic layer deposition by the described method of claim 1.

14., it is characterized in that wherein Zhi Bei film also is included in the other reacting precursor of introducing in the preparation process by the described method of claim 1, be used for mixing, realize the real-time doping of film.

15., it is characterized in that said doping comprises that at least PH3 and AsH3 realize that the n-type mixes by the described method of claim 14.

16., it is characterized in that said doping comprises that at least B2H6 realizes that the p-type mixes by the described method of claim 14.

17., it is characterized in that the doping of said feeding is passed in the reaction chamber by a kind of of reacting precursor who uses with atomic layer deposition at least together with reacting precursor by the described method of claim 14.

18., it is characterized in that the reacting precursor that the doping of said feeding is used with any atomic layer deposition with reacting precursor is not passed in the reaction chamber simultaneously by the described method of claim 14.

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